1. Field of the Invention
The present invention relates to a magnetic head assembly and, more particularly, to a magnetic head assembly which slides and comes into contact with a magnetic recording medium, thereby recording and reproducing information.
2. Related Background Art
Magnetic recording/reproducing systems are widely used to record and reproduce various information such as audio information in the case of tape recorders or the like, characters, numerical information, image information, and the like in the case of magnetic disk apparatuses.
In general, the magnetic recording and reproducing are performed by use of a magnetic recording medium such as a magnetic tape, magnetic disk, or the like serving to store information as a magnetic signal, and a magnetic head assembly for recording the information in the magnetic recording medium or reproducing the information therefrom, by converting the information from an electric signal to a magnetic signal or converting the information from a magnetic signal to an electric signal.
To transmit and receive the information between the magnetic head and the magnetic recording medium, the magnetic gap of the magnetic head to record or reproduce the information needs to be near the magnetic recording medium, as close as possible. The distance between the magnetic gap and the magnetic recording medium is called the spacing. When the spacing is large, both recording and reproducing efficiencies fairly deteriorate. For example, upon reproduction, the deterioration of the reproduced output due to the spacing, what is called a spacing loss Ls, is expressed by the following expression. EQU Ls=-54.6 d/.lambda.(dB) . . . (1)
Where d denotes the spacing and .lambda. indicates a wavelength of the reproduced signal.
From this expression, therefore, it will be understood that when .lambda. is 0.5 .mu.m, the output decreases by about 10 dB due to the increase in spacing d of merely 0.1 .mu.m. The amount of decrease in the output is determined by only the spacing, independently of the performance of the magnetic head and the magnetic recording medium.
Therefore, it will be appreciated that the spacing is more important than the magnetic head and magnetic recording medium in determining the performance of the whole magnetic recording system. In addition, in recent years, a signal of a shorter wavelength is used due to the requirement of high density. Therefore, as will be also understood from expression (1), it is more and more important to reduce the spacing as much as possible.
In general, when the head and medium having relative speeds approach each other, a substantial pressure is generated by the air lubricating layer the narrow gap between the head slide surface and the medium. Thus, in the case of the flexible magnetic recording medium such as a floppy disk or the like, the medium can be deformed so as to be balanced with the substantial pressure and the spacing distribution. Since the substantial pressure at this time depends on the shape of the head slide surface, the shape of the head slide surface is the significant factor when the spacing is set.
FIG. 1 shows the shape of a conventional video head for recording and reproducing information in and from one magnetic track.
A video head 1 is constituted by adhering a reinforcing plate 4 so as to sandwich a magnetic core 3. As shown in FIG. 2A, for instance, a head slide surface 2 is formed by cylindrically grinding the magnetic gap surface of a magnetic gap 5, or by another method. FIGS. 2A and 2B illustrate cross-sectional views of different structures of the magnetic gap portion in FIG. 1.
In the example of FIG. 2A, chamfered portions 7 are formed on both ends in the direction of the track width of the slide surface 2. Thus, the width w in the track direction of the head slide surface is narrowed and the area of the head slide surface is reduced, thereby decreasing the substantial pressure which will be generated in the air lubricating layer between the medium and the magnetic head and also minimizing the spacing. In the example of FIG. 2B, in place of the chamfers, notches 8 are formed in both edge portions in the direction of the track width, thereby obtaining a similar effect.
However, the foregoing conventional structures have the following problems. First, since corner portions 6 at the edges in the track direction of the head slide surface are likely to be abraded, these portions are abraded in association with the use of the head for a long time and the shape of the slide surface changes. Thus, there is a limitation on the use of these designs when the chamfers and notches are allowed to approach the track, and the degree of freedom in setting of the spacing is restricted. On the other hand, as shown in FIG. 2A, since the width w in the track width direction of the slide surface of the chamfered head is widened as the head is abraded, the spacing amount varies as the head is used. Further, in the case of the notched head as shown in FIG. 2B, although the width w does not change, the width itself of the core becomes small due to the notches 8, that there is the problem of a decrease in strength with respect to the weight in the lateral direction.
Although the examples of a one-channel head assembly for use with one track have been shown above, in the case of the magnetic head assembly having the channels for as many as two tracks, the slide surface itself is wide. Therefore, even when the chamfers and notches as shown in FIGS. 2A and 2B are formed, it is difficult to narrow the width w of the slide surface to a value according to a desired spacing condition. In particular, in the case of the head assembly for use with multitracks, the slide surface is fairly large; therefore, the spacing can be hardly effectively adjusted by the foregoing methods.